1. Field of the Invention
The present invention relates to an automatic electronic parts mounting apparatus and, more particularly, to an automatic electronic parts mounting apparatus in which when various chip type electronic parts (to be referred to as chip parts hereinafter), e.g., resistors, capacitors, and transistors are automatically positioned/mounted on a printed board placed on an X-Y table in a plurality of different types of patterns constituted by identical patterns and independent patterns having no correlation therewith chip parts having different shapes and sizes can be selectively positioned/mounted by sorting them in accordance with their forms.
2. Description of the Prior Art
In a conventional automatic electronic parts mounting apparatus of this type, as disclosed in, e.g., U.S. Pat. No. 4,653,664, chip parts having different shapes and sizes are selectively fed from a parts feed means in which they are stored in parts storage tapes wound around the respective tape reels in accordance with their forms and types, the fed chip parts are chucked by a plurality of suction nozzles, which are formed on the periphery of a rotary type index table, at predetermined suction positions, the index table is intermittently rotated so as to convey the chip parts to corresponding parts mounting positions on a printed board placed on an X-Y table, and the chip parts are automatically positioned/mounted at predetermined mounting positions on the printed board by moving the X-Y table in the X-Y directions. Apparatuses having such an arrangement have been developed and put into practical use.
An operation of such a conventional mounting apparatus is generally controlled by programs. In addition, in the above apparatus, when chip parts are mounted on a single printed board in a plurality of identical patterns by repeating the same pattern, and the same mounting operation is repeated in accordance with the same pattern formation direction.
For this reason, in the identical mounting patterns formed on the single printed board, the final parts mounting position of a given pattern and the initial mounting position of the next pattern may be greatly separated, and hence a considerably long period of time is required to move the X-Y table. In addition, since all the patterns formed on the printed board are oriented in the same direction, forming the patterns on the printed board is uniformly limited, and efficient patterning becomes impossible. Therefore, a large portion of a board material is wasted.
Recently, as various types of mounting patterns are produced in small quantities, various patterns tend to be formed in a single printed board. When a plurality of identical patterns and independent patterns having no correlation therewith are formed in a printed board by mounting various chip parts having different shapes and sizes together in this manner, since the above-described process in which the same pattern is repeatedly formed cannot be used, the identical patterns and the independent patterns are sorted, and positioning/mounting must be independently performed in units of sorted patterns, thereby extremely complicating the process.
In addition, when chip parts having different shapes and sizes are to be mounted on a single printed board together, if a large chip part or a chip part with a high center of gravity is mounted first, a positional error due to an inertial force tends occur because the frequency of movement of such a chip part upon high-speed movement of the X-Y table is higher than that of a small chip part or a chip part with a low center of gravity to be mounted next.